For the past three years, Britain’s defence chiefs have been forced to make big cuts in military capability in response to pressure on public spending. One area where there has been particularly lively debate is the future of the UK’s nuclear weapons. Between now and 2016, Britain must decide whether to spend £20bn building four new submarines that can carry Trident II missiles with nuclear warheads. The current fleet of Vanguard-class submarines that carry Trident is nearing the end of its service life. As the moment of decision approaches, debate on whether the nation can afford a like-for-like replacement for Trident has intensified.

The Financial Times believes Britain must retain its nuclear weapons capability. The ability to inflict "unacceptable damage" on a potential aggressor is the ultimate guarantee that Britain will not be invaded or destroyed. The possession of nuclear weapons is critical to the status of both Britain and France as Europe’s two leading military powers and as members of the UN Security Council. Recognising this, none of Britain’s three main political parties today advocates unilateral nuclear disarmament.

However, since 2010, the Liberal Democrats, the junior partners in the ruling coalition, have raised questions about Trident. They have pondered whether Britain might save money by relaxing the round-the-clock patrols conducted by the submarines carrying the missiles. They have even asked whether Britain might ditch Trident altogether and find a cheaper delivery system, one that involves, say, launching cruise missiles from multipurpose submarines. To help advance their arguments, the Lib Dems asked Britain’s Cabinet Office to publish a report setting out possible options.

The first thing to be said about the Cabinet Office report, published on Tuesday, is that it comprehensively demolishes the idea of ditching Trident for something else. The report concludes that any new system – whether launched from land, air or from multipurpose submarines – would mean designing a completely new warhead. This would take so long and be so costly that "any of the realistic alternative systems is ... more expensive" than the existing one.

The Lib Dems’ other argument – that Britain could stick with Trident but mount it on three submarines and not four – also attracts little support. The report states that the economies made by coming down to three submarines would be almost negligible – saving £56m a year during the 30-year life of the entire programme. Meanwhile, by abandoning “continuous-at-sea” deterrence, Britain’s ability to respond in a crisis would be undermined.

Building a replacement for Trident will be financially demanding. The £20bn cost of constructing the new submarines will consume at least a third of the Ministry of Defence equipment budget in the 2020s – potentially crowding out other naval and air programmes. Future governments must ensure that there is enough money available to maintain conventional military capabilities.

But the case for building a like-for-like replacement is now settled. The reality is that as the 2015 general election draws nearer, the Lib Dems have played politics with Trident. Their goal is to have a policy that separates them from the Conservatives and which appeals to the Lib Dems’ electoral base, one instinctively in favour of scrapping nuclear weapons altogether.

This newspaper might have had more respect for the Lib Dems on the future of Trident if they had publicly espoused the whole-hearted unilateralism to which many of their grass roots supporters are committed. Instead, they have embraced a weak, differentiated position at the cost of credibility.

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BRITAIN'S DETERRENT

Defence policy needs to insure against long-term risks, not only current threats. Replacing Trident with a comparable system makes strategic and financial sense

Editorial

The Times – 17 July 2013

"The answer to an atomic bomb on London is an atomic bomb on another great city," wrote Clement Attlee after the destruction of Hiroshima and Nagasaki in 1945. The new Prime Minister had immediately understood the logic of deterrence in the nuclear age. Britain's independent deterrent, the creation of the post-war Labour Government, remains the right policy for Britain in the 21st century. When the current Trident nuclear deterrent reaches the end of its lifespan, it should be replaced by an equivalent system guaranteeing a continuous-at-sea capability.

Not everyone agrees. Under the terms of its coalition agreement with the Conservatives in 2010, the Liberal Democrats pressed for a review of the options for replacing Trident. The report was published yesterday. Though it makes no recommendations, it carefully sets out the possible courses for defence policy after Trident. By implication rather than assertion, these make a convincing case for maintaining a force posture like the one Britain has at the moment. That is a position supported by the Conservatives. The other main parties should assent to it too.

Trident will be operational for several years yet. A final decision on its replacement is due in 2016, after the next general election. But it is not feasible to delay beyond that date, given the time needed to construct a successor fleet of submarines. Though much has changed since the Cold War, this does not mean that nuclear defence is outmoded.

Defence planning needs to cope with remote contingencies, not only current threats. It is highly likely that, by the middle of this century, the number of nuclear-armed states will be greater than it is now, and that these will include aggressive regimes. North Korea has conducted three nuclear tests. Iran has a history of constructing illicit facilities that make little sense for a civil nuclear programme, of lying about those capabilities and of making threats against other states.

A decision by Britain to give up its deterrent will not deflect such states from acquiring nuclear weapons. Keeping the deterrent may, in a crisis, impress upon an adversary the potentially suicidal costs of miscalculation. An independent British capability will ensure that an aggressor will be unable to intensify a crisis beyond this country's ability to control. Replacing Trident is prudent given the extreme long-term uncertainties about the international order, especially given Britain's distinctive role as one of few nations able and willing to engage in operations far beyond its shores.

If Britain is to have a nuclear stance, a submarine-based system is the best option. Basing missiles on land makes them vulnerable to a pre-emptive strike and thus reduces their effectiveness as a deterrent: Modifying the current Astute-class attack submarines to carry Cruise missiles would be a false economy: the missiles would be vulnerable to interception and have a shorter range.

The Lib Dems argue that a successor to Trident need not be a like-for-like replacement of the current fleet of four submarines. But four is the minimum needed to ensure that at least one boat is on patrol at any time. That is worth paying for.

First, acquiring Trident is good value at an estimated capital cost of between £20 billion and £25 billion. Second, the marginal cost of a third and fourth boat, once that initial investment has been made, will be comparatively low. Philip Hammond, the Defence Secretary, suggested yesterday that the saving from reducing the number of submarines would amount to less than 0.2 per cent of the defence budget. Third, if a crisis arose when Britain lacked a boat at sea, launching one might aggravate tension rather than defuse it.

Trident is an integral part of Britain's defence capability within NATO. It should be replaced – and the task should be done properly.